Johannesburg - Two senior cabinet ministers are embroiled in a row that threatens to spill into the courts, the Sunday Times reported.

According to the newspaper, Public Service Minister Lindiwe Sisulu has accused Defence Minister Nosiviwe Mapisa-Nqakula of lying about the number of flights Sisulu took between September 2009 and February 2012.

Letters and documents show Sisulu racked up an R11 million bill for chartered flights on a Gulfstream jet while she was defence minister, the newspaper reported.

Mapisa-Nqakula, in a written response to Parliament in October 2012, said Sisulu had taken 203 flights on the private jet. Sisulu has insisted she took only 35.

In an interview with the Sunday Times, Sisulu vowed to clear her name and confirmed she was considering legal action against her cabinet colleague.

“I want that expunged from my records with necessary apology and necessary remedy. I will not have it. I 've worked very hard for this government and my reputation is not going to be sacrificed on something silly like that.”

The newspaper reported it was in possession of nine letters about the issue sent between the offices of Sisulu, Mapisa-Nqakula and deputy president Kgalema MotlantheÄ as head of government business.

On November 9, 2012, Sisulu wrote to Mapisa-Nqakula:” The answer you gave was wrong and I am of the opinion that this was deliberate.”

She asked Mapisa-Nqakula to withdraw the answer.

On the same day Sisulu wrote to Motlanthe to insist Mapisa-Nqakula's answer was “not true”.

Mapisa-Nqakula through her spokeswoman Joy Peter said she would not respond to Sisulu's comments because she was dealing with the matter through Motlanthe's office.